* This updates all references to nuget.exe to use the copy in the root.
* This deletes all NuGet.config and NuGet.exe files that are not in the root.
* This removes all references to NuGet.targets (which is obsolete and no longer exists)

Rogjt mpw we build a boostrap version of csc and vbc and bootstrap
with those running on Mono. This commit switches us to build a CoreCLR
compatible csc and then running the boostrap on CoreCLR

Right now the full set of Linux CoreCLR runtime assemblies is not
available on NuGet, so we substitute with some assemblies we stash in
our NuGet ZIP package.

Diagnostics.csproj was under Roslyn/Diagnostics in solution, but everything there is removed and the only project referencing Diagnostics.csproj now is src/VisualStudio/VisualStudioDiagnosticsToolWindow/VisualStudioDiagnosticsWindow.csproj, so move Diagnostics.csproj under Roslyn/VisualStudio and remove Roslyn/Diagnostics from solution.

All the projects depend on this project are already moved to dotnet/roslyn-analyzers repo.

Everything under dotnet/roslyn/src/Diagnostics/FxCop is moved to dotnet/roslyn-analyzers/src/AnalyzerPowerPack .

Everything under dotnet/roslyn/src/Diagnostics/FxCop/Desktop.Analyzers is moved to dotnet/roslyn-analyzers/src/FxCop/Desktop.Analyzers.

Everything under dotnet/roslyn/src/Diagnostics/FxCop/System.Runtime.InteropServices.Analyzers is moved to dotnet/roslyn-analyzers/src/FxCop/System.Runtime.InteropServices.Analyzers.

Everything under dotnet/roslyn/src/Diagnostics/FxCop/System.Runtime.Analyzers is moved to dotnet/roslyn-analyzers/src/FxCop/System.Runtime.Analyzers.

Everything under dotnet/roslyn/src/Diagnostics/CodeAnalysis is moved to dotnet/roslyn-analyzers/src/CodeAnalysis.

Everything under dotnet/roslyn/src/Diagnostics/Roslyn is moved to dotnet/roslyn-analyzers/src/Roslyn.

Move TestUtilities.csproj and TestUtilities.FX45.csproj to separate directories to accomodate current nuget limitations

Update the DNX build tools, which fixes #3876. Now that the
bug is resolved, add the CoreCLR projects directly to the
compiler solutions.

Added one analyzer CA2153 into Desktop.Analyzer.
Addressed the code review comments and removed unused helper code.

This is the start of our unit test assembly for our MSBuild assets.

This change adds a couple sub folders (Features, Host, Repl, Setup) and moves BasicVisualStudioRepl back to Interactive.

It's confusing for new users to have the Roslyn solutions nested
inside the src/ directory and there's really no good reason those where
there in the first place. This moves them to the root directory, except
for the Toolset.sln solution, which is only for building Roslyn in CI
scenarios and has been moved to the build/ directory.

This deletes the empty and unused Desktop assemblies from the code base.

Three rules related to PInvokes are being moved here (CA1060, CA1401, CA2101).

The rules are fairly straightforward and dont branch out into C#\VB. The fixer for CA2101 needs to be able to fix DeclareSub statements in VB and needs language specific dlls.

# The first commit's message is:
Move csc2/vbc2 logic into csc/vbc behind '/shared' flag

This change adds support for the '/shared' flag to csc/vbc, which indicates
to the command line compiler that it should attempt to use the compiler server.

This change doesn't yet delete the csc2 and vbc2 binaries to preserve compatibility
for our partners until they have a change to switch to the new API.

# The 2nd commit message will be skipped:

#	Address CR comments

# The 3rd commit message will be skipped:

#	More CR comments